Conventionally, there has been known a charge-discharge system, which can charge an electric storage device mounted on a vehicle with (by) an electric power supplied from a power source (supply) external to the vehicle, and which can supply an electric power from the electric storage device mounted on the vehicle to an electric load external to the vehicle (including an electric storage device external to the vehicle, and the like). Supplying the electric power from the electric storage device mounted on the vehicle to the electric load external to the vehicle means discharging in terms of the electric storage device mounted on the vehicle. Accordingly, in the present specification, supplying the electric power to the electric load external to the vehicle may be expressed as “discharging to the electric load external to the vehicle.” Further, the electric storage device mounted on the vehicle may also be referred to as a “vehicle electric storage device”, and the electric storage device external to (outside of) the vehicle may also be referred to as en “external electric storage device,” Furthermore, the power source (supply) external to (outside of) the vehicle may also be simply referred to as an “external power source”, and the electric load external to (outside of) the vehicle” may also be simply referred to as an “external electric load.” The external electric storage device can be the external electric load as well as the external power source.
In the charge-discharge system described above, a control unit of the vehicle (control device mounted on the vehicle) controls the charge of the vehicle electric storage device using the electric power supplied from the external power source and the discharge of (from) the vehicle electric storage device to the external electric load.
Accordingly, the control unit of the vehicle needs to recognize/determines whether the charge of the vehicle electric storage device should be carried out using the electric power supplied from the external power source (that is, request for charge is being generated) or the discharge of (from) the vehicle electric storage device to the external electric load should be carried out (that is, request for discharge is being generated).
One of known arts is configured so as to supply the electric power from the external power supply to the vehicle electric storage device in response to a request from the vehicle, and so as to supply the electric power from the vehicle electric storage device to the external electric load in response to a request from an external equipment (e.g., device disposed inside of a house) (refer to Japanese Patent Application Laid-Open (kokai) No. 2009-303483).